6 - Synaptic Transmission Flashcards
0
Q
Chemical Synapses
A
- Provide directionality, amplification, excitation/inhibition, plasticity/remodeling, & spatial/temporal integration
- Increased intracellular Ca2+ is required and sufficient for NT release
- Enters through voltage-gated Ca2+ channels
- Decreased extracellular calcium results in decreased postsynaptic potentials
1
Q
Electrical Synapses
A
- Extremely fast and bidirectional passive flow of current between cells via gap junctions, which are non-selective
- not common in CNS
- very common in glial cell synapses
2
Q
Synaptic Facilitation
A
- Rapid increase in yah septic strength that occurs when to or more APs invade the presynaptic terminal within a few milliseconds of each other. The second EPSP is larger than the first because of prolonged elevation of presynaptic Ca2+ allowing more NT to be released
- ->NOT the same as temporal summation
- Small Molecule NTs and Peptide NTs are packaged into different vesicles and can be differentially released according to pattern of electrical stimulation
- Small Molecule NTs are packaged into Clear Vessicles docked in the Active Zone. Can be released with low frequency stimulation.
- Peptide NTs are a packaged into Dense Vesicles. Requires high frequency stimulation for release.
3
Q
Quantal Neurotransmitter Release
A
- Endplate Potential (EPP) is produced by the simultaneous release of many individual discrete packets of ACh, each producing a miniature EPP (MEPP)
- Fixed size of MEPP is consistent with Quantal release of NT
- Correspondence between a vesicle’s ACh content and MEPP size also is consistent with Quantal NT release
4
Q
Action Potential Transmission
A
- Most dendrites do not transmit APs because they don’t contain many Na+ channels and thresholds are too high
- Decremental Conduction due to leaky membrane prevents most EPSPs from reaching the cell body
- Simultaneous firing of many synapses raises the summated potential to threshold for excitation and elicits an AP
